Solvent extraction of mineral lubricating oils



D. 27, 1938. C. c. BUCHLER Er AL 2,141,511

SOLVENT EXTRACTION OF' MINERAL LUBRIGATING OILS Filed Feb. 1'7, 1936Figi ATTORN EY Patented Dec. 27, i938 FICE soLvEN'r ExTaAc'rroN or lLUBmcA'rrNG ons Cliiord C. Buchler and Sterling H. Diggs, Caspeir,

v Wyo., assignors to Standard @il Can11111.=`

. cago, my a cl'pomtiolli 0f Il 1 r. 111 t Application February 17,1936, Serial No. 64,202

8 Claims.

This invention relates to a process of refining mineral oils andspecifically petroleum lubricating oils of the type employed in thelubrication of internal combustion engines and commonly i', known asmotor oils. The invention further relates to a process of extractingsuchoils withv a specific solvent, namely; beta beta dichlor diethylether, hereinafter referred to as chlorether. The use of thissolvent'for the extrac- 1 tion' of mineral lubricating oils has beenpreviously described in United States Patent No.

2,003,238, entitled Process of separatingvmineral oils, by H. T.Bennett, filed June 23, 1933.

More particularly, the present invention relates s to an improvement inthe use of beta beta dichlor diethyl ether in lubricating oil extractionprocs esses, wherein undesirable naphthenic constituents are removedfrom the parainic component of the oil. One object of the invention isAto 1 facilitate the use ofv said Chlor-ether solvent in the extractionof wax-containing lubricating oil stocks. Another object of theinvention is to increase the selective solvent action of said solvent bythe addition of minor amounts of certain modi-l 5 fying agents. v

,In vthe extraction of Mid-Continent and Salt Creek lubricatingdistillates suchv as motor oil distillates falling within the viscosityrange of 20-60 S. A. E. number, dimculty has frequently 1 beenencountered with separation of waxin the extraction process. Where thedistillate contains over 5% of parafln wax and frequently as much as or15% thereof, the wax will usually crystallize in the form of a thickmush or magma at ordinary temperatures and even at temperatures in therange of 'V100-125 F. This is especially true of the heavier distillateswhich contain higher' 50 small amounts, usually not exceeding 20% andordinarily from 2 to 10%, which will .enable the extraction operation tobe conducted at higher temperatures. whereythe paraiiin wax contained inthe oil will remain in liquid condition and at 55 the same time asatisfactory separation of oil from solvent can be obtained withoutmaterially sacriiicing either yield or viscosity index. The substanceshaving this desirable property belong to the class of organic alkylhydroxy compounds, more particularly polyhydroxy alcohols such asthe-glycols. Examples of such compounds are ethylene glycol, propyleneglycol, butyleneglycol, di-ethylene glycol, tri-ethylene glycol andtrimethylene glycol; alcohols such as ethyl, propyl and butyl alcoholsmay be used but are not as satisfactory as the polyhydroxy alcoholsabove mentioned and also usually cause dimculty in handling due to theirrelatively low boiling points. The high boiling points of thepolyhydroxy al-` cohols make it possible to recover these materialsalong with the chlor-ether; losses by evaporation are substantially nil.

The solubility of ethylene glycol in anhydrous beta beta' dichlordi-ethyl ether is shown in the following table:

Pah-cent. ethylllene g co m an Tempmtul dix-,ous chloreg glycol mixtureno Trace 115.....1 2 120 4 130 5.2 1w l5.1i

When usingthis modifying agent, the amount to be added will preferablynot exceed that which will dissolve at the minimum temperature ofextraction, and in any case it will not exceed that 'whichy willdissolve at the highest temperature of mimng solvent and oil.

The eect of hydroxy allwl compounds in increasing the mlscibilitytemperature of oils and.

chiot-ether is'shown by an example in winch a Y lightoll having a specicgravity of .8338 (60 F.) was mixed with chlor-ether at 75 F. at whichItemperatureit was completely miscible with the solvent. Onthe additionof one volume of 95% ethy1^alcohol to the chlor-ether a separation ofthe oil was obtained without lowering the temperature.

` As an example of the eect of. glycol in improving the extraction of amineral lubricating oil with chlor-ether, a heavy lubricating distillateof S. A. E. 60 viscosity range was extracted with solvent in the ratioof two parts of solvent to one -part of oil, by volume, in a singlebatch application. One portion of oil was extracted with chlor- .etherat a temperature of 809 giving a. yield oi 83% oi' raiiinate having aviscosity index of 84.5.

Another portion of oil was extracted with chlorether saturated withethylene glycol at a temperature of 87 F., giving a yield of 83% ofrafnate having a viscosity index of 86. This illustrates the effect ofthe glycol inpermitting the extraction to be carried out at a highertemperature, giving substantially the same yield and actually improvingthe viscosity'index.

The drawing which forms a part of this specication illustratesgraphically the effect of certain modifying agents in the chlor-etherextraction process.

The effect of glycols in increasing the yield or rafiinate at highertemperatures is well illustrated by the graph shown in Eig. l where theyield of rafinate in percent by weight is plotted against thetemperature` of extraction in degrees Fahrenheit. The curves in thisgraph were obtained by extracting dewaxed lubricating distillate havinga viscosity in the range of S. A. E. 60, the wax having been removed inorder toavoid diiliculties in obtaining extraction at the lowertemperatures. 'The oil was extracted with two volumes of solvent in asingle application. 'I'he chart shows that for a given yield of ranatethere is a decided increase in the temperature of extraction; forexample, in order to obtain a yield of 76% under these conditions it isnecessary. to operate at a temperature of 1 08? F.' with pureChlor-ether. The addition of 4% propylene glycol permits obtaining thesame yield at a temperature of about 120 F. and the use of a saturatedsolution of ethylene glycol in the .dl-chlor ether increases thepermissible extraction temperature to about 123 F.

Fig.v 2 shows in a graphical way the eect of additions of glycols tochlor-ether with respect to the temperature of complete miscibility ofthe solvent with a. heavy mineral lubricating oil. The data given' inthis graph were obtainedl on the same oil as used in determining thedata. for

Fig. 1, i. e., a dewaxed distillate from Salt Creek' crude'having aviscosity in the range Lof 60 S. A. E. The ratio of solvent to 'oil wasvaried as indicated in the chart and glycols were added to the solventin an 'amount of 4%' by volume. From these results it will be seen that,employing a solvent ratio of 2 to 1, the temperature of completevmiscibility is raised from about 152 F. withv pure chlor-ether to'180.' F. with chlorether saturated with ethylene glycol. Propyleneglycol and di-ethylene glycol alsd raised the miscibility temperaturevery considerably when used in this amount.

To illustrate the advantage of this invention in overcoming difllcultywith wax separation, the extraction of av lubricating distillate fromSalt Creek crude (used in making SQA. E. 50 grade motor oil) may bereferred to. Such an oil becomes completely miscible with chlor-ether inall proportions at about 139 F. When the oil is cooled to cause anextract layer to separateit is found that solid wax begins to separateat about 128 F. In thetraction of this oil therefore it is usuallynecessary to maintain the operating temperaturelwithin a carefullycontrolled range of temperature if difculties from wax separcani arationare tobe avoided. When extracting in countercurrent towers theseparation of wax is most objectionable and a temperature range of only8 F. mustl be maintained with van oil such as above. Theaddition of thehydroxy alkyl compounds even in small 'proportions greatly alleviatesthese rigid operating requirements.

Having thus described our invention, what we claim is:

1. In the process of extracting undesirable 10 naphthenic constituentsvfrom wax-containing mineral hydrocarbon lubricating oils wherein the oilis intimately contacted with beta beta dichlor diethyl ether and theundesirable naphthenic constituents are removed as an extract in'solution in said ether, the improvement comprising incorporating insaid beta beta dichlor diethyl ether from 2 to 20% of an alkylene glycoland conducting the extraction at a temperature above the solidifyingpoint of the Wax-containing oil. l

2. The process of claim 1 wherein the alkylm glycol is ethylene glycol.

3. The process of claim 1 wherein said alkyiene glycol is diethyleneglycol.

4. In the process of extracting undesirable naphthenic constituents fromwax-containing mineral lubricating oils wherein the oil is intimatelycontacted with beta beta' dichlor diethyl ether and the undesirableconstituents are removed as an extract in solution in ,said ether, theimprovement comprising conducting the extraction at a temperature abovethe solidifying point of the oil and modifying the solvent action ofsaid beta beta dichlor diethyl ether by incorporating therein from 2 to7% of ethylene glycol before the contacting step. j

5. In the process of extracting mineral hydrocarbon lubricating oilscontaining parailln wax and undesirable naphthenic hydrocarbons with '40beta beta'vdichlor diethyl ether wherein the oil is intimately contactedwith the ether and the oil and ether, are separated into two phases inwhich the heavier ether phase contains dissolved4 undesirable naphthenichydrocarbon constituents of the oil, the improvement comprising avoidingdifficulties resulting from the separation of solid paraiiin wax as athird phase in the process by Aadding between 2% and 20% of a dihydroxyalkyl compound to the beta beta dichlor diethyl ether whereby themiscibility temperature of said ether and said lubricating oil is raisedsubstantially above the melting point of said waxy oil and conductingthe extraction at a temperature between the melting point of said waxyoil and the said raised miscibility temperature, whereby said wax isprevented from crystallizing as a separate phase from said mixtureduring the extraction operation.l

6. The process of claim 5-wherein the dihy- 60 droxy alkyl compound isethylene glycol.

7. The process of claim 5 wherein the dihydroxy alkyl compound is butylene glycol.

8. 'I'he process of claim 5 wherein the dihydroxy alkyl compound isdiethylene glycol.

- CLIFFORD C. BUCHLER.

STERLING H. DIGGS.

